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feat(mergeScan): add higher-order lettable version of mergeScan
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,133 @@ | ||
| import { Operator } from '../Operator'; | ||
| import { Observable } from '../Observable'; | ||
| import { Subscriber } from '../Subscriber'; | ||
| import { Subscription } from '../Subscription'; | ||
| import { tryCatch } from '../util/tryCatch'; | ||
| import { errorObject } from '../util/errorObject'; | ||
| import { subscribeToResult } from '../util/subscribeToResult'; | ||
| import { OuterSubscriber } from '../OuterSubscriber'; | ||
| import { InnerSubscriber } from '../InnerSubscriber'; | ||
| import { OperatorFunction } from '../interfaces'; | ||
|
|
||
| /** | ||
| * Applies an accumulator function over the source Observable where the | ||
| * accumulator function itself returns an Observable, then each intermediate | ||
| * Observable returned is merged into the output Observable. | ||
| * | ||
| * <span class="informal">It's like {@link scan}, but the Observables returned | ||
| * by the accumulator are merged into the outer Observable.</span> | ||
| * | ||
| * @example <caption>Count the number of click events</caption> | ||
| * const click$ = Rx.Observable.fromEvent(document, 'click'); | ||
| * const one$ = click$.mapTo(1); | ||
| * const seed = 0; | ||
| * const count$ = one$.mergeScan((acc, one) => Rx.Observable.of(acc + one), seed); | ||
| * count$.subscribe(x => console.log(x)); | ||
| * | ||
| * // Results: | ||
| * 1 | ||
| * 2 | ||
| * 3 | ||
| * 4 | ||
| * // ...and so on for each click | ||
| * | ||
| * @param {function(acc: R, value: T): Observable<R>} accumulator | ||
| * The accumulator function called on each source value. | ||
| * @param seed The initial accumulation value. | ||
| * @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of | ||
| * input Observables being subscribed to concurrently. | ||
| * @return {Observable<R>} An observable of the accumulated values. | ||
| * @method mergeScan | ||
| * @owner Observable | ||
| */ | ||
| export function mergeScan<T, R>(accumulator: (acc: R, value: T) => Observable<R>, | ||
| seed: R, | ||
| concurrent: number = Number.POSITIVE_INFINITY): OperatorFunction<T, R> { | ||
| return (source: Observable<T>) => source.lift(new MergeScanOperator(accumulator, seed, concurrent)); | ||
| } | ||
|
|
||
| export class MergeScanOperator<T, R> implements Operator<T, R> { | ||
| constructor(private accumulator: (acc: R, value: T) => Observable<R>, | ||
| private seed: R, | ||
| private concurrent: number) { | ||
| } | ||
|
|
||
| call(subscriber: Subscriber<R>, source: any): any { | ||
| return source.subscribe(new MergeScanSubscriber( | ||
| subscriber, this.accumulator, this.seed, this.concurrent | ||
| )); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * We need this JSDoc comment for affecting ESDoc. | ||
| * @ignore | ||
| * @extends {Ignored} | ||
| */ | ||
| export class MergeScanSubscriber<T, R> extends OuterSubscriber<T, R> { | ||
| private hasValue: boolean = false; | ||
| private hasCompleted: boolean = false; | ||
| private buffer: Observable<any>[] = []; | ||
| private active: number = 0; | ||
| protected index: number = 0; | ||
|
|
||
| constructor(destination: Subscriber<R>, | ||
| private accumulator: (acc: R, value: T) => Observable<R>, | ||
| private acc: R, | ||
| private concurrent: number) { | ||
| super(destination); | ||
| } | ||
|
|
||
| protected _next(value: any): void { | ||
| if (this.active < this.concurrent) { | ||
| const index = this.index++; | ||
| const ish = tryCatch(this.accumulator)(this.acc, value); | ||
| const destination = this.destination; | ||
| if (ish === errorObject) { | ||
| destination.error(errorObject.e); | ||
| } else { | ||
| this.active++; | ||
| this._innerSub(ish, value, index); | ||
| } | ||
| } else { | ||
| this.buffer.push(value); | ||
| } | ||
| } | ||
|
|
||
| private _innerSub(ish: any, value: T, index: number): void { | ||
| this.add(subscribeToResult<T, R>(this, ish, value, index)); | ||
| } | ||
|
|
||
| protected _complete(): void { | ||
| this.hasCompleted = true; | ||
| if (this.active === 0 && this.buffer.length === 0) { | ||
| if (this.hasValue === false) { | ||
| this.destination.next(this.acc); | ||
| } | ||
| this.destination.complete(); | ||
| } | ||
| } | ||
|
|
||
| notifyNext(outerValue: T, innerValue: R, | ||
| outerIndex: number, innerIndex: number, | ||
| innerSub: InnerSubscriber<T, R>): void { | ||
| const { destination } = this; | ||
| this.acc = innerValue; | ||
| this.hasValue = true; | ||
| destination.next(innerValue); | ||
| } | ||
|
|
||
| notifyComplete(innerSub: Subscription): void { | ||
| const buffer = this.buffer; | ||
| this.remove(innerSub); | ||
| this.active--; | ||
| if (buffer.length > 0) { | ||
| this._next(buffer.shift()); | ||
| } else if (this.active === 0 && this.hasCompleted) { | ||
| if (this.hasValue === false) { | ||
| this.destination.next(this.acc); | ||
| } | ||
| this.destination.complete(); | ||
| } | ||
| } | ||
| } |